In this paper, electrostatically configurable 2D tungsten diselenide (WSe2) electronic devices are demonstrated. Utilizing a novel triple‐gate design, a WSe2 device is able to operate as a tunneling ...field‐effect transistor (TFET), a metal–oxide–semiconductor field‐effect transistor (MOSFET) as well as a diode, by electrostatically tuning the channel doping to the desired profile. The implementation of scaled gate dielectric and gate electrode spacing enables higher band‐to‐band tunneling transmission with the best observed subthreshold swing (SS) among all reported homojunction TFETs on 2D materials. Self‐consistent full‐band atomistic quantum transport simulations quantitatively agree with electrical measurements of both the MOSFET and TFET and suggest that scaling gate oxide below 3 nm is necessary to achieve sub‐60 mV dec−1 SS, while further improvement can be obtained by optimizing the spacers. Diode operation is also demonstrated with the best ideality factor of 1.5, owing to the enhanced electrostatic control compared to previous reports. This research sheds light on the potential of utilizing electrostatic doping scheme for low‐power electronics and opens a path toward novel designs of field programmable mixed analog/digital circuitry for reconfigurable computing.
By electrostatically tuning channel doping profiles, a triple‐gated 2D tungsten diselenide (WSe2) device can be operated as a diode, a tunneling or a metal‐oxide‐semiconductor field‐effect transistor (TFET/MOSFET). The best subthreshold swing among TFETs and the best ideality factor in diodes based on homogeneous 2D materials are reported. Self‐consistent simulations quantitatively agree with experiments and provide design guidelines for optimal performance.
Ultrascaled WS 2 field-effect transistors (FETs) fabricated on exfoliated multilayer channels with excellent ON-state and OFF-state performance are reported. Recorded high ON-state current ...(<inline-formula> <tex-math notation="LaTeX">{I}_{ \mathrm{\scriptscriptstyle ON}} </tex-math></inline-formula>) and ultralow contact resistance (<inline-formula> <tex-math notation="LaTeX">{R}_{C} </tex-math></inline-formula>) were achieved in a double-gated FET at a scaled overdrive voltage (<inline-formula> <tex-math notation="LaTeX">{V}_{OV}\boldsymbol = {V}_{GS}\boldsymbol -{V}_{TH} </tex-math></inline-formula>), reaching >600 (<inline-formula> <tex-math notation="LaTeX">\boldsymbol \mu \text{A}/\boldsymbol \mu \text{m} </tex-math></inline-formula>) normalized to footprint at <inline-formula> <tex-math notation="LaTeX">{V}_{DS}\boldsymbol =1 </tex-math></inline-formula> V and <inline-formula> <tex-math notation="LaTeX">{V}_{OV}\boldsymbol =2 </tex-math></inline-formula> V with a <inline-formula> <tex-math notation="LaTeX">{R}_{C}~\sim ~500 </tex-math></inline-formula> (<inline-formula> <tex-math notation="LaTeX">\Omega \times \mu \text{m} </tex-math></inline-formula>). We report statistics of more than 50 FETs with varying channel lengths, showing excellent OFF-state behavior with small threshold voltage (<inline-formula> <tex-math notation="LaTeX">{V}_{TH} </tex-math></inline-formula>) variations, near-ideal subthreshold slope (SS), and small drain-induced barrier lowering (DIBL). Various channel thicknesses (<inline-formula> <tex-math notation="LaTeX">{T}_{CH} </tex-math></inline-formula>) ranging from 2.1 to 7 nm were carefully evaluated in terms of short channel effects (SCEs) and ON-state current, and a WS 2 body thickness of 2.1 nm (three layers, the thinnest in our statistics) shows the best performance in both ON-state and OFF-state.
We demonstrate that a pure nitric oxide treatment at elevated temperatures provides a stable p-doping for monolayer WSe 2 . This approach allows achieving record high hole current densities of ...~<inline-formula> <tex-math notation="LaTeX">300 \mu \text{A} / \mu \text{m} </tex-math></inline-formula> and low contact resistances of <inline-formula> <tex-math notation="LaTeX">\sim 950 \Omega \cdot \mu \text{m} </tex-math></inline-formula>, while preserving the transistor on/off current ratio ><inline-formula> <tex-math notation="LaTeX">2\times 10 </tex-math></inline-formula> 6 . This scalable pathway significantly improves the performance of p-type WSe 2 transistors, opening new opportunities for advancing 2D integration.
Schottky barrier (SB) transistors operate distinctly different from conventional metal‐oxide semiconductor field‐effect transistors, in a unique way that the gate impacts the carrier injection from ...the metal source/drain contacts into the channel region. While it has been long recognized that this can have severe implications for device characteristics in the subthreshold region, impacts of contact gating of SB in the on‐state of the devices, which affects evaluation of intrinsic channel properties, have been yet comprehensively studied. Due to the fact that contact resistance (RC) is always gate‐dependent in a typical back‐gated device structure, the traditional approach of deriving field‐effect mobility from the maximum transconductance (gm) is in principle not correct and can even overestimate the mobility. In addition, an exhibition of two different threshold voltages for the channel and the contact region leads to another layer of complexity in determining the true carrier concentration calculated from Q = COX * (VG–VTH). Through a detailed experimental analysis, the effect of different effective oxide thicknesses, distinct SB heights, and doping‐induced reductions in the SB width are carefully evaluated to gain a better understanding of their impact on important device metrics.
Mobility overestimation extracted from 2‐terminal measurement is investigated, which is attributed to impacts of contact gating of Schottky barrier in the on‐state of devices. Comprehensive analysis including impacts of effective oxide thickness of gate dielectrics, different TMD channel materials, and an involvement of extrinsic doping schemes are provided to gain a better understanding of their impacts on important device metrics.
Tunneling field-effect transistors (TFETs) have emerged as a potential candidate to outperform conventional metal-oxide-semiconductor FETs at low voltages, since their operation mechanism can ...overcome the fundamental subthreshold swing (SS) limit of 60 mV/decade at room temperature. We report carbon nanotube (CNT) based TFETs with abrupt p-i-n tunneling junctions controlled by electrostatic doping. Minimum SS (SSmin) of ∼41 mV/dec is observed with nearly no temperature dependence, as clear evidence of the TFET operation. We further investigate devices using CNTs with smaller bandgaps, reporting a record high band-to-band tunneling (BTBT) current of ∼100 nA for a single CNT. Non-linear output characteristics are observed as expected for devices operating outside of the quantum capacitance limit (QCL). Overall, electrostatically doped CNT TFETs shine a promising path for low-power electronic applications.
Triple-gate CNT TFET implemented with thin gate dielectric for record high BTBT current with SSmin< 60mV/dec. Display omitted
•First study of carbon nanotube TFET performance comparison for channel material with different bandgaps.•Record high band-to-band tunneling current with sub-60 mV/dec switching for carbon nanotube TFET.•Triple-gate TFET implementation utilizing thin gate dielectric to achieve high band-to-band tunneling efficiency.
The prevalence of mitral valve prolapse (MVP) among middle- and older-aged individuals is estimated to be 2-4% in Western countries. However, few studies have been conducted among Asian individuals ...and young adults. This study included a sample of 2442 consecutive military adults aged 18-39 years in Hualien, Taiwan. MVP was defined as displacement of the anterior or posterior leaflet of the mitral valve to the mid portion of the annular hinge point > 2 mm in the parasternal long-axis view of echocardiography. Cardiac chamber size and wall thickness were measured based on the latest criteria of the American Society of Echocardiography. The clinical features of participants with MVP and those without MVP were compared using a two-sample t test, and the cardiac structures were compared using analysis of covariance with adjustment for body surface area (BSA). Eighty-two participants were diagnosed with MVP, and the prevalence was 3.36% in the overall population. Compared with those without MVP, participants with MVP had a lower body mass index (kg/m
) (24.89 ± 3.70 vs. 23.91 ± 3.45, p = 0.02) and higher prevalence of somatic symptoms related to exercise (11.0% vs. 4.9%, p = 0.02) and systolic click in auscultation (18.3% vs. 0.6%, p < 0.01). In addition, participants with MVP had greater left ventricular mass (gm) and smaller right ventricular wall thickness (mm) and dimensions (mm) indexed by BSA than those without MVP (149.12 ± 35.76 vs. 155.38 ± 36.26; 4.66 ± 0.63 vs. 4.40 ± 0.68; 26.57 ± 3.99 vs. 25.41 ± 4.35, respectively, all p-values < 0.01). In conclusion, the prevalence and clinical features of MVP in military young adults in Taiwan were in line with those in Western countries. Whether the novel MVP phenotype found in this study has any pathological meaning needs further investigation.
Scaling of monolayer transition metal dichalcogenide (TMD) field-effect transistors (FETs) is an important step toward evaluating the application space of TMD materials. Although some work on ...ultrashort channel monolayer (ML) TMD FETs has been published, there exist no comprehensive studies that assess their performance in a statistically relevant manner, providing critical insights into the impact of the device geometry. Part of the reason for the absence of such a study is the substantial variability of TMD devices when processes are not carefully controlled. In this work, we show a statistical study of ultrashort channel double-gated ML WS2 FETs exhibiting excellent device performance and limited device-to-device variations. From a detailed analysis of cross-sectional scanning transmission electron microscopy (STEM) images and careful technology computer aided design (TCAD) simulations, we evaluated, in particular, an unexpected deterioration of the subthreshold characteristics for our shortest devices. Two potential candidates for the observed behavior were identified, i.e., buckling of the TMD on the substrate and loss of gate control due to the source geometry and the high-k dielectric between the metal gate and the metal source electrode.
Background: The early diagnosis of pulmonary embolism (PE) remains a challenge. Electrocardiograms (ECGs) and D-dimer levels are used to screen potential cases. Objective: To develop a deep learning ...model (DLM) to detect PE using ECGs and investigate the clinical value of false detections in patients without PE. Methods: Among patients who visited the emergency department between 2011 and 2019, PE cases were identified through a review of medical records. Non-PE ECGs were collected from patients without a diagnostic code for PE. There were 113 PE and 51,456 non-PE ECGs in the training and validation sets for developing the DLM, respectively, and 27 PE and 13,105 non-PE cases in an independent testing set for performance validation. A human-machine competition was conducted from the testing set to compare the performance of the DLM with that of physicians. Receiver operating characteristic (ROC) curves, sensitivity, and specificity were used to determine the diagnostic value. Survival analysis was used to assess the prognosis of the patients without PE, stratified by DLM prediction. Results: The DLM was as effective as physicians in diagnosing PE, with 70.8% sensitivity and 69.7% specificity. The area under the ROC curve of DLM was 0.778 in the testing set and up to 0.9 with D-dimer and demographic data. The non-PE patients whose ECG was misclassified as PE by DLM had higher all-cause mortality hazard ratio (HR) 2.13 (1.51-3.02) and risk of non-cardiovascular hospitalization HR 1.55 (1.42-1.68) than those correctly classified. Conclusions: A DLM-enhanced ECG system may prompt PE recognition and provide prognostic outcomes in patients with false-positive predictions.
BACKGROUND: The B-type natriuretic peptide (BNP) and N-terminal pro-brain natriuretic peptide (pBNP) are predictors of cardiovascular morbidity and mortality. Since the artificial intelligence ...(AI)-enabled electrocardiogram (ECG) system is widely used in the management of many cardiovascular diseases (CVDs), patients requiring intensive monitoring may benefit from an AI-ECG with BNP/pBNP predictions. This study aimed to develop an AI-ECG to predict BNP/pBNP and compare their values for future mortality. METHODS: The development, tuning, internal validation, and external validation sets included 47,709, 16,249, 4001, and 6042 ECGs, respectively. Deep learning models (DLMs) were trained using a development set for estimating ECG-based BNP/pBNP (ECG-BNP/ECG-pBNP), and the tuning set was used to guide the training process. The ECGs in internal and external validation sets belonging to nonrepeating patients were used to validate the DLMs. We also followed-up all-cause mortality to explore the prognostic value. RESULTS: The DLMs accurately distinguished mild (≥500 pg/mL) and severe (≥1000 pg/mL) an abnormal BNP/pBNP with AUCs of ≥0.85 in the internal and external validation sets, which provided sensitivities of 68.0–85.0% and specificities of 77.9–86.2%. In continuous predictions, the Pearson correlation coefficient between ECG-BNP and ECG-pBNP was 0.93, and they were both associated with similar ECG features, such as the T wave axis and correct QT interval. ECG-pBNP provided a higher all-cause mortality predictive value than ECG-BNP. CONCLUSIONS: The AI-ECG can accurately estimate BNP/pBNP and may be useful for monitoring the risk of CVDs. Moreover, ECG-pBNP may be a better indicator to manage the risk of future mortality.
Cardiovascular events such as myocarditis following mRNA COVID-19 vaccination are increasing. We present a 67-year-old postmenopausal woman with Takotsubo Syndrome and Graves' disease after mRNA ...COVID-19 vaccination. She developed chest pain and shortness of breath one week after vaccination. An electrocardiogram revealed ST elevation in the precordial leads. Coronary angiography revealed the absence of obstructive coronary artery disease, and the left ventriculography showed a typical feature with apical ballooning. Laboratory workup showed the elevation of free T4 and thyrotropin receptor antibodies. It was presumed that Takotsubo Syndrome and Graves' disease were probably related to the COVID-19 mRNA vaccination. The patient was treated with low-dose bisoprolol, diuretics, carbimazole, and steroid and discharged uneventfully. The mRNA COVID-19 vaccination is still safe and effective to defend against COVID-19 pandemic. However, clinicians should be aware of the possible cardiovascular adverse events other than myocarditis following vaccination.
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